The present invention relates to a skin-whitening cosmetic material with which skin blackening or skin pigmentation such as spots and freckles due to UV rays is removed, reduced (whitened) or prevented.
Dyspigmentation is one symptom of skin aging, which gives spots such as chloasmata (liver spots) and senile spots. It is known that dyspigmentation is exacerbated by ultraviolet rays. To prevent dyspigmentation, used are UV protectors. To relieve dyspigmentation which has already produced spots, used are skin-whitening cosmetic materials comprising, as the active ingredient, any of vitamin C, placenta extract, kojic acid, arbutin, unsaturated fatty acids, etc. Of those, it is known that unsaturated fatty acids such as typically linoleic acid or linolic acid have an excellent effect of reducing or whitening pigmentation caused on the skin (see the Journal of the Cosmetician Association of Japan, Vol. 27, pp. 415-423, 1993).
However, skin-whitening cosmetic materials comprising unsaturated fatty acids such as linoleic acid or linolic acid are problematic in that the endermic absorption of unsaturated fatty acids having been applied to the skin is often prevented by the barrier function of the skin with the result that the skin-whitening cosmetic materials applied to the skin could not exhibit so much the effect of reducing or whitening pigmentation to the degree as expected. Therefore, in order to make them exhibit a high skin-whitening effect, skin-whitening cosmetic materials must contain a large amount of unsaturated fatty acids, but cause unfavorable skin troubles.
Some reports are known, which disclose emulsified cosmetics (see Japanese Patent Application Laid-Open (JP-A) Hei-5-70332) or liniments for external use (JP-A Hei-5-70334) comprising unsaturated fatty acids, phospholipids, and proteins or their decomposates; and skin-treating and protecting agents comprising unsaturated fatty acids, phospholipids and vitamin E (see JP-A Sho-61-40210). However, the skin-whitening effect of those known materials is poor.
On the other hand, it is well known that liposomes are effective as carriers. For example, known are liposomes comprising linoleic acid or linolic acid as the active ingredient, which are said effective for acne, blackheads, pimples, pustules, etc. (see Published Japanese translation of PCT international publication for patent application (JP-W) Hei-7-509001). However, the stability of the cosmetic materials comprising such liposomes is not satisfactory, and the effective amount of linoleic acid or linolic acid to be in those liposomes is at least 1% by weight or more. Thus, it is hard to say that know liposome exhibit a sufficient effect at a low concentration of the active ingredient.
Accordingly, an object of the present invention is to provide a skin-whitening cosmetic material which comprises, as the active ingredient, an unsaturated fatty acid or a derivative thereof, which is highly effective for reducing or whitening pigmentation caused on the skin even in a lower concentration of the active ingredient and is highly safe.
We, the present inventors have assiduously studied in order to attain the object noted above, and, as a result, have found surprisingly that a skin-whitening cosmetic material comprising phospholipids, antioxidants, proteins or their decomposates, muco-polysaccharides or their salts, along with unsaturated fatty acids such as linoleic acid or linolic acid exhibits an excellent effect for reducing or whitening skin spots even though it contains a reduced amount of unsaturated fatty acids, and that the safety of the material is high. On the basis of these findings, we have completed the present invention.
Specifically, the invention provides a skin-whitening cosmetic material comprising;
(A) at least one member selected from unsaturated fatty acids having from 18 to 22 carbon atoms and having from 2 to 6 double bonds in the molecular structure, and their derivatives,
(B) a phospholipid,
(C) an antioxidant,
(D) at least one member selected from proteins and their hydrolyzates, and
(E) at least one member selected from muco-polysaccharides and their salts.
Preferably, the skin-whitening cosmetic material of the invention comprises liposomal composites of those ingredients (A) to (E).
The invention also provides a skin-whitening cosmetic material comprising liposomal composites of the ingredients (A) to (E).